Rotational control device

ABSTRACT

A rotational control device for the setting of angles in actuators, in particular of a restricting device used for determining the flow cross-section in a flow line for internal combustion engines, has an electrical setting motor with a two-pole status and a two-pole permanent magnet rotor. To obtain a robust setting motor, which is technically easy to manufacture in a compact construction, the stator poles are designed as claw poles and the stator winding is located as a toroidal coil in a ring space formed by the claw poles and a ring casing which is coaxial with these, for the magnetic return path. The stator winding is energized by a d.c. supply, with reversible current direction. The magnetic resistances in the magnetic return path and across the claw poles are calibrated such that in the event of a currentless stator winding, the permanent magnet rotor engages in the pole gaps between the claw poles.

STATE OF TECHNOLOGY

The invention is based on a rotational control device for setting theangle of regulating elements, in particular on a restricting device usedfor determining the flow cross-section in a flow line for internalcombustion engines.

In a known control device of this type (DE 38 30 114 A1), the two statorpoles used to generate the magnetic reset moment in the event of acurrentless setting motor are designed asymmetrical with a pole widthsignificantly deviating, one from the other in the circumferentialdirection. The rotor poles, which are designed as shell shaped magnetsegments, are arranged asymmetrically on the rotor and extend in eachcase circumferentially over an angle greater than 90°, in whicharrangement the smaller pole width of the stator pole measured on thecircumference is approximately equal to the angle over which the rotorpoles extend. The stator winding, as a cylindrical coil, embraces amagnetic return path loop which connects the two stator poles with eachother. Such a rotational control device involves high manufacturingcosts due to the pronounced asymmetry.

ADVANTAGES OF THE INVENTION

In contrast, the control device in accordance with the invention has theadvantage of a setting motor of compact construction which is easilymanufactured in terms of production technology and in which the magneticmoment is sufficiently large to return the throttle element, in theevent of a currentless setting motor, to its starting position whichexposes a defined minimum aperture cross-section. The setting motor isrobust and has low susceptibility to faults. By operating the statorwinding with a direct current with reversible current direction, e.g.via an end stage which can supply both current directions, an adequatelysized rotor setting angle is achieved between the closing position ofthe restricting device, at which the exposed aperture cross-section ofthe flow line is zero, and the end position of the restricting device,at which the exposed aperture cross-section of the flow line is maximum.

The magnetic engagement on the pole gaps between the two claw poles ofthe rotor, i.e. its magnetic return moment in the event of a currentlessstator winding, can be strengthened by providing arched recesses in thecentral region of the front face connections of claw poles and ringcasing in accordance with a first embodiment of the invention. Thisresults in a reduction of the cross-section in the magnetic return path,so that the ratio of the magnetic resistances in the return path and intransverse direction of the claw poles, which determines the magnitudeof the engagement moment, is increased.

The magnetic engagement on the pole gaps can alternatively bestrengthened by the air gap under the claw poles being dimensioned inaccordance with a preferred embodiment such that the radial air gapwidth in the central region of the claw poles is larger than in the edgezones of the claw poles, viewed in circumferential direction.

In a preferred embodiment of the invention, the magnet material for thepermanent magnet rotor is hard ferrite or plastic bonded ferrite orplastic bonded neodymium iron boron. By comparison with the rare earthmagnet material, a substantial reduction of the manufacturing costs isachieved. The rotor may have a cylindrical permanent magnet withdiametric magnetisation direction, which accommodates the rotor shafttorsionally rigid in a central axial bore, or is pivoted on a stub axle,or it may have two shell shaped magnet segments which are fixed on acylindrical carrier which is connected to the rotor shaft. The radialmagnetisation direction in the two magnet segments extends in one magnetsegment from the outside inwards and extends in the other magnet segmentfrom the inside outwards. The attachment of the permanent magnet or ofthe permanent magnet segments on the rotor shaft or on the carrierconnected with the rotor shaft is in both cases preferably by means ofplastic moulding.

A stator design which is simple in terms of production technology can beachieved in that the stator in accordance with a further embodiment ofthe invention consists of two identically designed stator parts, eachhaving a claw pole and which after relative rotation in the separatingplane, and after relative rotation of 180°, in a plane of rotation whichextends along the stator axis at right angles to the separating plane,are joined in a separating plane which is aligned at right angles to thestator axis.

DRAWING

The invention is explained in more detail by means of embodimentexamples shown in the drawing and by the description below. Theillustrations show:

FIG. 1 a longitudinal cross-section of a rotational control device foran internal combustion engine;

FIG. 2 a schematic exploded view of a setting motor without a winding,in the rotational control device of FIG. 1;

FIG. 3 a view of the rotational control device in the direction of thearrow III in FIG. 2; and

FIG. 4 a similar presentation as in FIG. 3 of the setting motor inaccordance with a further embodiment example.

DESCRIPTION OF THE EMBODIMENT EXAMPLES

The rotational control device shown in longitudinal cross-section inFIG. 1 is used for the control of the aperture cross-section of a bypassline 10 around a schematically represented throttle 11 in the inductionpipe 12 of an internal combustion engine for the purpose of idling speedcontrol. The rotational control device has an actuator housing 13, whichis made of plastic material, in which a long flow channel 17 is formed,the aperture cross-section of which is controllable by a restrictingdevice 14 which is designed as a rotary valve. The restricting device 14is actuated by setting motor 15, which is accommodated in a motorhousing 16. The motor housing 16 is adjoined to the actuator housing 13at right angles to the axis of the same, with the restricting device 14,together with a control part 141 penetrating the flow channel 17transversely through an arc shaped breakthrough 131 in the actuatorhousing 13.

The setting motor 15, in a manner generally known, comprises a stator 18with stator winding 19 held on the motor housing 16, and a permanentmagnet rotor 20 which is coaxial with the stator, in which the rotor islocated torsionally rigid on the rotor shaft 21, which itself issupported, rotatable, at bearing points 22,23 on the actuator housing 13and on the motor housing 16, respectively. The throttle element 14 islocated with a fixing part 142 torsionally rigid on the rotor shaft 21.The throttle element 14 is made as one piece with the control part 141and the fixing part 142, of plastic material, with the fixing on therotor shaft 21 being effected by injection moulding to the rotor shaft21 during injection moulding of the throttle element 14.

Two claw poles 24,25 are arranged on the stator 18, offset against eachother by 180° in circumferential direction, which are connected onopposing front faces to a ring casing 26 which encompasses the clawpoles 24,25 with radial clearance, for the magnetic return path. Locatedin the ring space which is limited by the ring casing 26 and the clawpoles 24,25 is the stator winding 19 which is formed as a toroidal coiland which is wound on a spool carrier 36 of plastic material. Tofacilitate simple mounting of the stator winding 19 with the spoolcarrier 36, the stator 18 is made of two identically constructed statorportions 181 and 182, which is illustrated in particular in FIG. 2. Thetwo stator portions 181,182 are adjoined in a separating plane 28 whichis aligned at right angles in relation to the stator axis 27, namely, onthe one hand, after one stator portion 182 has been rotated in theseparating plane 28 by 180° relative to the first stator portion 181,and on the other hand, additionally by 180° relative to the first statorportion 181 in a rotational plane which extends along the stator axis 27at right angles in relation to the separating plane 28. The compositestator 18 is shown in FIG. 1, where the different stator parts have beenmade identifiable by different hatching. A front view of the stator 18and the rotor 20 in the direction of the arrow III in FIG. 2 is shown inFIG. 3. The two claw poles 24,25, positioned opposite each other by 180°can be clearly seen.

The rotor 20 carries a cylindrical permanent magnet 29 with diametricmagnetisation direction, schematically shown in FIG. 3. The materialused for the magnet is hard ferrite or plastic bonded ferrite or plasticbonded neodymium iron boron. The permanent magnet 29 with a centralaxial bore 30 is pushed over the rotor shaft 21, and during theinjection moulding of the throttle element 14, it is moulded onto therotor shaft 21, so that the permanent magnet 29 is located torsionallyrigid on the rotor shaft 21. For a so-called currentless emergencyoperation of the rotational control device, during which the throttleelement 14 must expose a predetermined minimum aperture cross-section inthe flow channel 17 of the actuator housing 13, an engagement of therotor 20 on the pole gaps 31,32 between the claw poles 24,25 is effectedin the event of a currentless stator winding 19, by means of appropriatecalibration of the magnetic resistances in the magnetic return path. Therestricting device 14, being assigned to the rotor 20, is then fixed onthe rotor shaft 21 such that it exposes the desired minimum aperturecross-section in the flow channel 17.

A strong engagement of the rotor 20 on the pole gaps 31,32 is achievedby providing an arc shaped recess 33 and 34, respectively, in the middleregion of the frontal connections of the claw poles 24,25 to the ringcasing 26. Due to the arc shaped recesses 33,34, the cross-section inthe magnetic return path is significantly reduced, thereby markedlyincreasing the ratio of the magnetic resistances in the magnetic returnpath and in transverse direction of the claw poles 24,25, which is ofdeterminant importance for the size of the return moment. The statorwinding 19 is energised by a direct current with reversible currentdirection. This can be effected, for example, by connecting the statorwinding 19 via a connecting plug 35, which is formed as one piece withthe plastic motor housing 16, to an end stage which can supply bothcurrent directions.

In a further embodiment of the stator 18, shown in FIG. 4, the strengthof engagement of the rotor 20 on the pole gaps 31,32 is achieved byreducing the air gap 37 at the edges of the claw poles 24,25. In thisarrangement, the claw poles 24,25 are designed such that the radial airgap width in the central region of the claw poles 24,25 is larger thanin the two edge zones of the claw poles 24,25, viewed in circumferentialdirection. The magnetic air gap resistances at the claw pole edges arethus lower than at the claw pole centre, which leads to the increase ofthe return moment for the rotor 20 in the event of a currentless statorwinding 19, albeit that this advantage is obtained at the expense of arestricted setting angle of the rotor 20, which amounts to approximately40° in the embodiment example of FIG. 4. However, due to the possibilityof moving the rotor 20 in inverse rotating directions, the totalpossible setting angle for the restricting device 14 is adequate for thepurpose of its application in internal combustion engines.

The invention is not restricted to the described embodiment examples.The rotor can, for example, have two shell-shaped permanent magnetsegments which are fixed on a cylindrical carrier and which have aradial magnetisation direction. The magnetisation direction of onemagnet segment on the rotor is from the outside inwards, and themagnetisation direction of the other is from the inside outwards. Thecylindrical carrier for the magnet segments is connected to the rotorshaft torsionally rigid. The fixing of the magnet segments on thecarrier is again by plastic injection moulding.

We claim:
 1. A rotational control device for setting the turning angleof actuators, in particular on a restricting device used for determiningthe flow cross-section in a flow line for internal combustion engines,comprising an electric setting motor, having a stator with two statorpoles and a stator winding and a two-pole permanent magnet rotor whichis designed such that in the event of a currentless stator winding, areturn torque acts on the permanent magnet rotor, pulling the magnetrotor back to its starting position, and with a torsionally rigidcoupling of the restrictive device to the rotor such that in the rotor'sstarting position, the restrictive device exposes a predeterminedminimum restriction cross-section in the flow line, the stator poles aredesigned as claw poles (24, 25), which, on opposing front faces are eachconnected to a ring casing (26) which encompasses the claw poles (24,25) with a radial clearance, for the magnetic return path, the statorwinding (19) is located as a toroidal coil in a ring space formed by thering casing (26) and the claw poles (24, 25) and can be energized by adirect current with reversible current direction, and that the magneticresistances in the magnetic return path and transverse to the radialaxes of the claw poles (24, 25) are dimensioned such that in the eventof a currentless stator winding (19), the permanent magnet rotor (20)engages on the pole gaps (31, 32) between the claw poles (24, 25).
 2. Arotational control device in accordance with claim 1, in which areshaped recesses (34, 35) are provided on the central region of the frontface connections of the claw poles (24, 25) and the ring casing (26). 3.A rotational control device in accordance with claim 1, in which theclaw poles (24, 25) are designed such that a width of a radial air gapwidth (37) between each claw pole (24, 25) and the permanent magnetrotor (20) in the central region of the claw poles (24, 25) is greaterthan in the two edge zones of the claw poles (24, 25).
 4. A rotationalcontrol device in accordance with claim 1, in which a hard ferrite,plastic bonded ferrite or plastic bonded neodymium iron boron is used asthe material for the permanent magnet rotor (20).
 5. A rotationalcontrol device in accordance with claim 2, in which a hard ferrite,plastic bonded ferrite or plastic bonded neodymium iron boron is used asthe material for the permanent magnet rotor (20).
 6. A rotationalcontrol device in accordance with claim 3, in which a hard ferrite,plastic bonded ferrite or plastic bonded neodymium iron boron is used asthe material for the permanent magnet rotor (20).
 7. A rotationalcontrol device in accordance with claim 1, in which the permanent magnetrotor (20) has a cylindrical permanent magnet (29) which accommodates arotor shaft (21) in an axial bore (30).
 8. A rotational control devicein accordance with claim 2, in which the permanent magnet rotor (20) hasa cylindrical permanent magnet (29) which accommodates a rotor shaft(21) in an axial bore (30).
 9. A rotational control device in accordancewith claim 3, in which the permanent magnet rotor (20) has a cylindricalpermanent magnet (29) which accommodates a rotor shaft (21) in an axialbore (30).
 10. A rotational control device in accordance with claim 4,in which the permanent magnet rotor (20) has a cylindrical permanentmagnet (29) which accommodates a rotor shaft (21) in an axial bore (30).11. A rotational control device in accordance with claim 1, in which thepermanent magnet rotor (20) has a cylindrical permanent magnet (29)which is supported torsionally rigid on a stub axle which penetrates anaxial bore (30) of the permanent magnet (29).
 12. A rotational controldevice in accordance with claim 2, in which the permanent magnet rotor(20) has a cylindrical permanent magnet (29) which is supportedtorsionally rigid on a stub axle which penetrates an axial bore (30) ofthe permanent magnet (29).
 13. A rotational control device in accordancewith claim 3, in which the permanent magnet rotor (20) has a cylindricalpermanent magnet (29) which is supported torsionally rigid on a stubaxle which penetrates an axial bore (30) of the permanent magnet (29).14. A rotational control device in accordance with claim 4, in which thepermanent magnet rotor (20) has a cylindrical permanent magnet (29)which is supported torsionally rigid on a stub axle which penetrates anaxial bore (30) of the permanent magnet (29).
 15. A rotational controldevice in accordance with claim 1, in which the permanent magnet rotorhas two shell shaped magnet segments which are fixed on a cylindricalsupport with radial magnetization direction in both, with themagnetization direction of one magnet segment extending from an outsideinwards and that of the other magnet segment extending from an insideoutwards.
 16. A rotational control device in accordance with claim 2, inwhich the permanent magnet rotor has two shell shaped magnet segmentswhich are fixed on a cylindrical support with radial magnetizationdirection in both, with the magnetization direction of one magnetsegment extending from an outside inwards and that of the other magnetsegment extending from an inside outwards.
 17. A rotational controldevice in accordance with claim 3, in which the permanent magnet rotorhas two shell shaped magnet segments which are fixed on a cylindricalsupport with radial magnetization direction in both, with themagnetization direction of one magnet segment extending from an outsideinwards and that of the other magnet segment extending from an insideoutwards.
 18. A rotational control device in accordance with claim 4, inwhich the permanent magnet rotor has two shell shaped magnet segmentswhich are fixed on a cylindrical support with radial magnetizationdirection in both, with the magnetization direction of one magnetsegment extending from an outside inwards and that of the other magnetsegment extending from an inside outwards.
 19. A rotational controldevice in accordance with claim 1, in which the stator (18) comprisestwo identically constructed stator parts (181,182), each having a clawpole (24,25) and which after relative rotation in a separating plane(28), and after relative rotation of 180° , in a plane of rotation whichextends along the stator axis (27) at right angles to the separatingplane (28), are joined in separating plane (28) which is aligned atright angles to the stator axis (27).